There are a number of situations in which it is helpful to predict the reactions of people to items they have not yet had the opportunity to sample. It is particularly useful to make recommendations for items to which people have wholly subjective reactions and which require a substantial investment of time or money to review, such as movies, books, music, and games. Difficulty arises because the actual reaction of a person to such an item can only be determined after money and time are invested in sampling the item.
The desirability of making recommendations for subjectively appreciated items is evidenced by the prevalence of movie critics, book reviewers, and other critics who attempt to appraise such items. However, the uniqueness of each item hinders objective comparison of the items relative to the response they will elicit from each individual. Short synopses or reviews are of limited value because the actual satisfaction of an individual depends upon his reaction to the entire rendition of the item. For example, books or movies with very similar plots can differ widely in style, pace, mood, and other characteristics. Moreover, knowledge beforehand of the plot or content can lessen enjoyment of the item.
It is common to study the advice of professional critics, but it is difficult at best to find a critic whose taste matches the taste of a particular individual. Using a combination of critics provides more information, but correctly combining and interpreting multiple opinions to extract useful advice is quite difficult. Even if a satisfactory combination is achieved, the opinions of professional critics frequently change over time as the critics lose their enthusiasm or become overly sophisticated.
Public opinion polls attempt to discern the average or majority opinion on particular topics, particularly for current events, but by their nature the polls are not tailored to the subjective opinions of any one person. Polls draw from a large amount of data but are not capable of responding to the subjective nature of a particular individual.
All of the above techniques require research by an individual, and the research is time consuming and often applied to out-of-date material. An individual is provided little help in making an optimal choice from a large set of largely unknown items.